Probably of foreign origin; fine wheaten flour -- fine flour.
Thayer's Greek Lexicon
Strong's 4585: σεμίδαλις
σεμίδαλις, accusative σεμίδαλιν, ἡ, the finest wheaten flour: Revelation 18:13. (Hippocrates, Aristophanes, Josephus, others; the Sept. often for כֹּלֶת.)
Revelation 18:13 - N-AFS GRK:ἔλαιον καὶ σεμίδαλιν καὶ σῖτον NAS: and olive oil and fine flour and wheat KJV: oil, and fine flour, and wheat, INT: oil and finest flour and wheat